In a vehicle air-conditioning apparatus applied to an electric vehicle, a hybrid vehicle, etc., as one of heat medium heating apparatuses that heat a heated medium used as a heat source for heating, there has been known a heat medium heating apparatus using a PTC heater in which a positive temperature coefficient (hereinafter referred to as a PTC device) is used as a heat generating element. As for such heat medium heating apparatus, PTL 1 discloses a heat medium heating apparatus configured such that an inside of a housing including an inlet and an outlet for a heat medium is partitioned into a number of heat chambers and heat medium circulation chambers by partition walls, and that the heat medium flowing through the circulation chamber is heated by means of a PTC device inserted and installed on a heat chamber side so as to be brought into contact with the partition walls.
PTL 2 discloses a heat medium heating apparatus configured such that an electrode plate, an insulation layer, and a heat transfer layer are provided on both surfaces of a PTC device sandwiching the PTC device to thereby configure a plate-like PTC heater, a pair of heat medium flow boxes are layered that includes an inlet and an outlet for a heat medium on both surfaces of the PTC heater and that are communicated with each other, and such that a substrate housing box is disposed on an external surface of the pair of heat medium flow boxes. PTLs 3 and 4 disclose a layered heat exchanger configured such that a burring is formed around a communication hole of a header section (tank section) provided on both ends of a tube element, alignment at the time of stacking is made easier by fitting the burring, and such that poor bonding due to position deviation at the time of bonding is prevented.
PTL 5 discloses a layered cooler in which a plurality sets of flat cooling pipes through which a cooling medium is flowed are layered so as to sandwich both surfaces of an electronic component, wherein an expandable communication member is connected to an opening of the cooling pipe to thereby communicate between the openings of the adjacent cooling pipes, and a rib is provided at a specific peripheral section of the opening to set a compressive strength of the cooling pipe in a thickness direction to be sufficiently large with respect to a load applied at the time of manufacturing of a layered cooler.